The present invention relates generally to an elevator counterweight.
Elevator counterweights on the one hand serve the purpose of loading the support means, which drive the elevator car, at the cable end not fastened to the car so that the drive pulley of the elevator drive, over which the support means is looped, can transmit the requisite friction force to the support means. On the other hand, they have the task of providing compensation for a part of the overall load, which is to be moved by the elevator drive and consists of the car weight and the useful load, in order to be able to reduce the required drive power.
Such elevator counterweights are produced in various forms. For example, they can consist of a metal plate or of a container filled with metal scrap or sand. In most cases, however, the elevator counterweight is formed from a metal frame in which metal plates are inserted and fixed.
Elevator counterweights are usually equipped with guide shoes by which they are guided at guide rails mounted in the elevator shaft. Guide shoes can be executed as slide guide shoes or as roller guide shoes.
Since the weight of the elevator counterweight is normally designed so that it is heavier than the empty elevator car, the risk exists, for example in the case of a defect at the drive brake or of a drive gear failure, that the elevator counterweight accelerates the elevator car upwards in uncontrolled manner so that the car hits the ceiling of the elevator shaft. In order to be able to reliably avoid such a situation, elevator counterweights are often equipped with safety brake devices which stop the elevator counterweight and thus also the elevator car when the permissible downward speed is exceeded.
In addition, safety specifications exist which oblige the counterweights of elevator installations to be equipped with safety brake devices when spaces, which can be used, are present below the elevator shaft.
An elevator counterweight with counterweight frame, inserted weight elements, slide guide shoes and safety brake devices is shown in the European patent document EP 0 757 659. As apparent from FIGS. 1 and 2, the counterweight has a simple, rectangular metal profile member frame in which metal plates are held and fixed. At lower extensions of the vertical frame profile members two slide guide shoes are fastened at one side and two safety brake devices are fastened at the other side, which co-operate with associated counterweight guide rails.
Such a construction of an elevator counterweight has certain disadvantages. Guide shoes and safety brake devices are mounted at the outer side of the counterweight frame. This has the consequence that on the one hand the detachable connections between the lower crossbar and the vertical frame profile members, as well as between the latter and the safety brake devices, has to be executed to be very rigid so that the inertia forces and weight forces, which arise during safety braking, of the counterweight can be safely transferred to the safety brake devices and that on the other hand a relatively large intermediate space between the frame and the counterweight guide rails cannot be used for placement of the weight elements. This is the case especially when the guide shoes are constructed as roller guide shoes and, due to the relatively large roller diameter, demand a considerable amount of installation space. Moreover, a significant part of the installation space of the elevator counterweight is lost due to the fact that the space between the lower extensions, which are present for fastening of the guide shoes and the safety brake devices, of the vertical frame profile members cannot be utilized as an installation space for weight elements.
In elevator installations where no safety brake devices are provided at the counterweight, either the lower extensions are too long, so that installation space is wasted, or different extensions are required, which increases the variety of components and the risk of incorrect deliveries.